The election of Mr. Trump ushered in a wave of political activism on the left, pushing millions of neophytes into the streets for protests and marches. A flood of groups formed, promising to oppose the president at every turn, return the House and Senate to Democratic control next year and protect undocumented immigrants and voting rights.

Many in this army of volunteers, however, were not thinking about this year, when two states will choose governors. But with Election Day on Nov. 7 drawing closer, the campaigns of Mr. Murphy in New Jersey and Lt. Gov. Ralph S. Northam, the Democratic candidate in Virginia, are seeing a surge in volunteers, many of them coming from anti-Trump groups.

In New Jersey, Action Together, with 18,000 members, has been coordinating its volunteers with the Murphy campaign’s effort to help Democrats up and down the ballot. NJ 11th for Change, a super PAC dedicated to unseating Representative Rodney Frelinghuysen, a Republican, has been canvassing, staffing phone banks and organizing a ground game on behalf of Mr. Murphy.

In Virginia, Let America Vote, a political action group founded by Jason Kander, a Democrat who lost a Senate race in Missouri, to defend voting rights, has coordinated its nationwide network of volunteers and activists with Mr. Northam’s campaign. They’ve dispatched more than 100 interns and have them canvassing and calling voters to support a candidate few knew anything about before joining the group.

Taehan Lee, 20, had never heard of Mr. Northam when he was stunned by Mr. Trump’s victory. Born in South Korea and having grown up in California, Mr. Lee was interested in national issues. To combat an administration he opposed, he applied for an internship with Let America Vote.

“I didn’t really ever see myself being involved in a campaign setting or working on something involved in a campaign,” Mr. Lee said. “But after last year’s election, I think a lot of us college students really want to get involved. I wanted to make a difference in politics and campaigns as soon as I could.”

So he packed his bags and headed to Virginia, where he spent 10 weeks over the summer “making calls, recruitment calls or volunteer voter calls,” “knocking on doors in 10 legislative districts” and eventually “learning how to interpret the data we got from the field” and incorporating it into electronic voter files.Many smaller, local groups providing waves of volunteers to the Democratic campaigns in New Jersey and Virginia are part of a broader, loosely connected network of so-called Indivisible groups.

Started by two former congressional aides who witnessed the rise of the Tea Party and its effectiveness at battling President Obama’s agenda, the Indivisible network began as an online guide for anti-Trump protesters on how to influence Congress.

Since then, it has mushroomed into more than 6,000 groups around the country. While many focused initially on lobbying local officials, they, too, have shifted toward the statewide efforts.

“A lot of groups don’t really see a major strategic shift between advocating for their elected officials, and if they’re not listening, pivoting toward electoral work,” said Leah Greenberg, 31, one of the co-founders of the Indivisible network.

Many smaller Indivisible groups share a similar origin story: what started as discussions around kitchen tables after the presidential election spawned public meetings, which attracted even greater attendance and eventually led to organizing into groups dedicated to taking specific action.

One Indivisible group in New Jersey — SOMA Action — decided not to make an endorsement in the governor’s race but has concentrated on promoting “broad progressive issues.” But those efforts include phone banking, canvassing and voter registration drives that will inevitably help the Murphy campaign.

The surge of volunteers for Mr. Murphy comes as polls show his campaign with a significant lead over Ms. Guadagno, the Republican candidate, but he is struggling with an electorate that is not particularly engaged in the governor’s race. A recent poll from Rutgers University found that about four in 10 voters do not know either candidate.

“These groups have not only galvanized the grass roots, they are driven entirely by grass-roots volunteers,” said Mr. Murphy, citing the palpable energy these volunteers have brought to his effort. “People with a newfound recognition that while voting is important, it is not sufficient.”

For Ms. Anderson, and the now 18,000 people who make up Action Together New Jersey, that has meant venturing far outside her comfort zone. While she initially said she wanted to just help out “behind the scenes,” she is now knocking on strangers’ doors or making calls for Mr. Murphy.